Abstract
The kinematic constraints on interacting nucleons in Large Hadron Collider (LHC) heavy-ion collisions are investigated in the framework of the Heavy Ion Jet Interaction Generator (HIJING) code incorporated with a collective cascade recipe. The latter is used to implement energy-momentum conservation constraints on both primary and secondary interacting nucleons. It is found that the energy-momentum conservation constraints on the interacting nucleons affect the whole charged-particle pseudorapidity density distribution (dN(ch)/d(eta)), at different centralities [from central (0-5%) to peripheral (70-80%) collisions], in Pb + Pb collisions at root s(NN) = 2.76 TeV. In particular, the kinematic constraints on the interacting nucleons are shown to reduce (dN(ch)/d(eta)) yield at mid-pseudorapidity (vertical bar eta vertical bar < 2) in all centrality intervals, which is consistent with the LHC data. In addition, the model predicts an enhancement of the hadron production at vertical bar eta vertical bar > 8, which could be checked in the future ALICE Zero Degree Calorimeter. Such an enhancement is found to be mainly due to the interactions of protons at the spectator parts of the collision. This indicates that the kinematic constraints are important for a correct geometrical treatment of Pb + Pb collisions at LHC energies.